United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research  Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-85/031  May 1985
Project  Summary
                                                                          '/ I '
Co-Firing  of  Solid  Wastes  and
Coal  at  Ames:  Pulverized  Coal
A. W. Joensen, J. L. Hall, J. C. Even, D. Van Meter,
P. Gheresus, G. Severns, S. K. Adams, and R. W. White
  The objectives of this research were
to conduct an in-depth evaluation of
the  environmental,  economic,  and
technical aspects of the resource and
energy  recovery system  in  Ames,
Iowa. The system includes recovery of
ferrous  metals,  preparation, storage,
and cofiring of the refuse-derived fuel
(RDF) with  coal  in the power plant
owned by the City of Ames to pro-
duce electric power.
  The  evaluation  period was  three
years, and this report covers the third
year of research. It includes evalua-
tions  of  the refuse processing plant
operation,  economics  of  the total
system  and individual  subsystems,
flow stream characterization, and per-
formance and   environmental  emis-
sions  of the suspension-fired steam
generator. Data  acquired during the
first year's evaluation were previously
reported  in  "Evaluation of the Ames
Solid Waste Recovery System. Part I-
Summary of Environmental Emissions:
Equipment,  Facilities,  and  Economic
Evaluations" (EPA-600/2-77-205).
  This  Project Summary was devel-
oped  by EPA's  Hazardous  Waste
Engineering Research Laboratory, Cin-
cinnati, OH,  to announce key findings
of the research  project that is fully
documented in a separate  report of
the same title  (see Project Report
ordering information at back).

Introduction
  The  Ames solid  waste recovery system
is a continuously  operating system that
processes municipal solid waste  (MSW)
to produce a shredded RDF that is burned
with Iowa-Western coal mixtures in the
tangentially fired steam generator in the
Ames municipal power plant. This system
consists  of  a  nominal  136-Mg/day
(150-ton/day)  process plant,  a 454-Mg
(500 ton) Atlas storage  bin,  pneumatic
transport systems,  and the power plant
boiler. The process plant incorporates two
stages of shredding, ferrous metal recov-
ery,  and an  air classification  (density)
separator.
  The full report presents results and con-
clusions of  the third-year  effort of an
evaluation of the Ames solid waste recov-
ery system, including  the process plant
studies and boiler environmental and ther-
mal  performance characterizations.  The
detailed study  objectives are listed in  the
following section.
  This evaluation is a major research pro-
gram funded by the Environmental Pro-
tection Agency (EPA) and the Department
of Energy (DOE). Project tasks are being
performed jointly by the City of Ames,
Iowa, the Engineering Research Institute
(ERI) of Iowa State University, the Ames
Laboratory/DOE,  and MRI.  The EPA
funding was used to provide for all man-
power, major field equipment  purchases,
power plant and process plant modifica-
tions, laboratory analyses of process plant
stream  characterization, and other sup-
plies used in the evaluation of both the
power plant  and process plant. The DOE
funding was used to provide laboratory
analysis of all field samples procured from
the power plant testing. Additional finan-
cial support was provided by ERI, the City
of Ames, and the American Public Power
Association.

System Description
  The Ames solid waste recovery system
consists  of three major subsystems: the
process plant, the Atlas storage bin, and
the existing steam generators of the mu-
nicipal power plant which were modified

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to burn RDF.  A general  flow  diagram is
shown in  Figure 1.  The MSW enters  the
45.4 Mg/h  process line  where primary
shredding,  ferrous  removal, and  second
stage shredding occurs.   The  RDF pro-
duced  from  the  air  density  separator
(ADS)  is  transported  152.4  m  to  the
454-Mg Atlas storage bin through a 36  cm
diameter pneumatic transport line.  Rejects
are subjected  to further  ferrous removal
and  are  then  trucked  to  the  municipal
landfill.
  The  RDF is  reclaimed from the storage
bin by four bucket sweeps which drop  the
material into two infeed conveyors for  the
pneumatic transport 61 m to  the  power
plant through two, 20 cm  diameter pipes.
The RDF is injected into the two opposite
corner  burners of the 35-MW tangentially
fired steam generator. The RDF is burned
as  a supplemental fuel  along with  the
Iowa-Western coal mixture in suspension,
and  RDF dropout material is burned on a
bottom  hopper  dump  grate installed  in
1978.
  The tangentially fired boiler (No.  7) is a
Combustion Engineering  Company, Type
VU-40S steam  generator  using balanced
draft operation with a  Ljungstrom  regen-
erative air heater  and an  ESP but  no
economizer. The two-drum  unit operates
                    at  5,860.8 kPa  and 485°C  steam quality
                    and 163,296 kg/h of steam flow.
                      Combustion air is drawn from the upper
                    part of the building, passed through the
                    forced  draft fan through the  air heater,
                    and enters the furnace through the corner
                    burner  assemblies via  two main wind-
                    boxes.  Flue gases produced by  the fuel
                    combustion in the furnace  pass  over the
                    primary and secondary superheater tube
                    banks through  the convection bank, the
                    air  heater,  and  then   through  the
                    American-Standard ESP and the induced
                    draft  fan  (both  located   outside  the
                    building). The flue gases are  discharged
                    out the 61-m  chimney or stack. Boiler
                    pump discharge feed water is used for
                    superheated steam temperature  control,
                    and this spray  water is injected  between
                    the primary and secondary superheater
                    sections.


                    Process Plant  Paniculate
                    Emissions and Dust  Evaluation
                      Particulate emissions from the roof ven-
                    tilators  of the refuse plant were evaluated
                    by EPA Method 5 particulate sampling
                    techniques.  Extensions  were  added  to
                    each of the roof ventilators on the refuse
                    plant to facilitate the samplng.  Twenty-
four sampling locations on  each of two
perpendicular   traverses   across  the
diameter of the roof ventilator ducts were
used, for a total of 48 sample points. At
each sample point, the sampling train was
operated for 3 min, meaning that a total
sample  was  collected over  144  min of
operation. The amount of particulate col-
lected  was then determined on  both a
volume and a time basis. The results are
reported later  in  this summary  under
Power Plant Emission Characterization.
  In addition  to  sampling emissions from
the roof ventilators, high volume ambient
air  samplers were  placed in the plant to
determine  the  dust  concentration  at
specific locations.
  The ambient air in the refuse processing
plant was sampled at three general eleva-
tions in the plant  by  means of high vol-
ume samplers modified to contain  10 cm
(4  in.)  diameter quartz  fiber  filters  on
which  the particulate matter collected as
the sample train operated.  Each sample
train was operated for 15 min. The weight
of  sample was  then  determined  for  the
time span of  the  test and  recorded  for
each location in  the plant.
  The three levels sampled in the plant in-
cluded the floor  level in the general vicini-
ty of the first and second stage shredders
   Municipal
  Solid Waste
Shredder
                                    Ferrous -*-
                           Non-Ferrous Separation
               Rejects •<-
               Non-Ferrous -<-
               Aluminum -^	
                                                                         Heavy Rejects
                                                                       Air Density Separation
                                                                         (Air Classification)
                                                                                                                       •Air
                                                                                  Combustible
                                                                                  Refuse Derived Fuel
                        Ames Municipal Power Plant
                     Stoker Fired Boiler - 7.5 MW
                     Stoker Fired Boiler - 12.5MW
                     Pulverized Coal Fired Boiler - 35 MW
                                                                               RDF
                                                                               Iowa and Colorado Coal
Figure 1.    Flow diagram of the Ames solid waste recovery system.

                                     2

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and   below  the  air  density  separator
(ADS).  The  mid-level location sampling
was adjacent to the ADS and underneath
the  bucket  elevator  in the  processing
plant. Upper level samples  were taken at
a walkway in the plant and at the top of
the bucket elevator.
  Following the weighing of the samples,
several representative filters were analyzed
to ascertain  the typical elements present
in the dust and the amounts. The amount
of dust in the ambient air of the process-
ing plant and the results of the trace  ele-
ment analysis  are also presented under
Power Plant  Emission Characterization.


Power Plant
  In this  study,  it was determined  that
two  major factors could be controlled at
various  levels.  These factors  were  the
steam generator load,  based  either  on
steam flow generated or  megawatts  of
power generated, and the amount  of
RDF, based on  heat energy input to  the
boiler. The levels chosen were 60, 80, or
100% nominal steam  generator load, and
0, 10, or  20%  RDF.  To obtain sufficient
data for statistical analysis,  a factorial  ex-
perimental  design  with  three replications
was  devised for the steam  generators, as
summarized  in  Table 1.  The  statistical
design was a 3 by 3 (three loads, three
values of EOF,  and three replications)  full
factorial experiment with 27 runs.  To as-
certain  compliance  with  Iowa's  Envi-
ronmental  Quality rules, additional mis-
cellaneous testing was done. During these
tests, the  location of the  RDF injection
point was changed.
  To satisfy the  objectives of the  en-
vironmental  emission  study,  all   ap-
propriate   input  and  output  streams
associated  with  the  operation  of   the
steam generator unit  were  sampled.  A
block diagram showing the sample loca-
tions of entering and leaving streams is in-
cluded as  Figure 2. The tests on unit No.
7 are summarized in Table 1. All inputs to
and  outputs from the steam  generator
were evaluated, including  fuel, combus-
tion  air, bottom ash,  steam, fly ash, and
stack gas. All  the  sampling was con-
ducted  on  a regular basis except  the
organic  species, which were sampled on
intermittent days as  manpower,   instru-
mentation,  and equipment would allow.


Economic Evaluation
  For 1976, 1977, and 1978, total  annual
expenses  remained relatively constant in
that the decreasing principal and  interest
were approximately balanced by  the in-
Table 1.    Test Matrix for Unit No. 7 Experimental Runs
Percent """»» nur
Load
60%
80%
100%
80%
(Wyoming coal)
100%
(Wyoming coal)
100%
(Wyoming coal)
0%
3 runs
(1976)
3 runs
(1976)
3 runs
(1976)
3 runs
(1978)
3 runs
(1978)
—
10%
—
2 test runs
(1977)
-
3 runs
(1978)
3 runs
(1978)
—
20%
—
-
-
3 runs
(1978)
3 runs
(1978)
Compliance resfs8
4 runs
(1978)
"RDF injection nozzles relocated to below the coal injection nozzle.
creasing  operating  and   maintenance
costs.
  Table 2 shows the  relative percentages
of operating and  maintenance costs al-
located to salaries, contractual expense,
commodities, and principal  and interest.
Contractual  expenses  were  higher  than
salaries during  all three years.  Principal
and  interest accounted for nearly half of
the  operating  and  maintenance  costs.
Total operating cost per  megagram aver-
aged $27.82 in  1976 and $23.87 in  1977.
Net  cost per megagram  averaged $12.47
in 1978, compared with $15.73 in  1976
and  $12.61 in 1977. These data are sum-
marized in Table 3.


Process Plant Emission
Characterization
  The  paniculate effluent from the  ven-
tilator ducts on  the refuse  plant and the
particulate in the ambient air of the pro-
cess plant were sampled by appropriate
methods.
  Table  4  summarizes  the  particulate
emissions from  the three roof ventilators
in operation during this  study. Over the
144-min  sampling  period,  the sampling
train filters collected particulate effluent in
the amounts shown.  It should be noted
that  the emission levels were very low
and, in fact, were virtually invisible to
observers.


Power Plant Emission
Characterization
  The average of heating values, ultimate
analysis, and trace elements analysis for
both coal and RDF used during the tests
on unit No. 7 are as follows: The ash con-
tent of the RDF was higher than that of
the coal  used during 1978, and both the
heating values and the amount of sulfur in
the RDF  were lower than that of the coal
for  the comparison runs made during  this
study.  The significance of these observa-
tions is that as the amount of refuse used
in the  boiler unit is increased an increased
amount of ash will  be generated due to
the use of refuse.  The additional amount
of ash was expected to show  up partially
as  fly  ash and  partially  as bottom ash.
Consequently, as the RDF increased,  the
amount of particulate emissions was ex-
pected  to increase. This was  also  in
agreement with the previous data  ob-
tained  on traveling grate  stoker unit Nos.
5 and  6 during 1976 and 1977 studies on
the traveling grate units.
  Because the sulfur content in the RDF
was lower than that in the coal,  it was
also expected that  the oxides and  sulfur
emitted from  the smokestack would  de-
crease significantly with increases in RDF.
  Based  on the tabulation  of  trace  ele-
ments  from the fuel samples,  the RDF
contained significantly more copper, lead,
titanium,   and  zinc  than  coal  used as a
fuel. As a consequence, the emissions of
these four elements  were expected  to in-
crease significantly.  The most  important
of the three elements would be the lead
because  of  its toxicity.  Therefore,  some
additional ambient air sampling was per-
formed on a random basis during the 1978
experiments. Germanium, iron,  and  sulfur ,
were found in smaller concentrations in
the RDF  than in the coal, but there  did

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    Flow Rate
    Ultimate Analysis
    Heating Value
    Chemical A nalysis
      & Trace Elements
    Ash Softening Temperature
Filter Particulate
  Trace Elements
Impinger Water Trace
  Elements
Emission Rates of
  Particulate
                                                                        Particulate Trace
                                                                          Elements
                                                                        Impinger Water Trace
                                                                          Elements
                                                                        Emission Rates of Particulate
                                                                          and Gaseous Species
                                                                        Particulate Sizing
  Humidity
  Barometer
  Intake
    Temperature
   Volume Flow
   Density
   Ultimate Analysis
   Heating Value
   Chemical A nalysis
     & Trace Elements
   Ash Softening
     Temperature
                                       Flow Rate
                                       Chemical Analysis &
                                         Trace Elements
                                       Softening Temperature
                                                                                       Flow Rate
                                                                                       Chemical Analysis &
                                                                                         Trace Elements
                                                                                       Softening Temperature
Figure 2.    Sampling locations.
Table 2.    Solid Waste Plant Operating Expense Distribution,  1976-1978
     Operating and maintenance           Principal and
Labor       Contractual    Commodities     interest
Year
                                                                           Total
1976
1977
1978*
Average
13.91
18.91
16.73

29.16
24.40
29.25
53.52
6.50
9.21
9.98

50.43
47.48
44.04
46.48
100
100
100
100
"January to September data only.
 Tabl«3.    Total Operating Expenses and Revenues for the Ames Solid Waste Recovery
           Processing Plant,  1976-1978
Year
1976
1977
1978"
Total
operating
expense
($)
1,033, 186
1,047,734
784,740
Total
revenue
1$)
448,721
494,309
411,190
Total
net
cost
1$)
584,465
553,425
373,550
Refuse
processed
IMg)
37, 137
43.890
29.958
Total
cost/Mg
t$/Mg)
27.82
23.87
26.19
Net
cost/Mg
l$/Mgl
15.73
12.61
12.77
'January through September only.
                                         not appear  to  be a significant difference
                                         between  RDF  and coal  in  the  relative
                                         amounts of the other elements.
                                           The uncontrolled emissons  generally in-
                                         crease with  RDF  except for  the  100%
                                         load data using  coal  only. Otherwise all
                                         the runs show  significant increases in par-
                                         ticulate emissions as the amount of RDF
                                         increases.  It is also  apparent from  this
                                         plot that the  initial data  obtained using
                                         coal only on this  boiler in 1976 and 1977
                                         indicate  a reverse trend in terms  of  par-
                                         ticulate  emissions.  The  expected   par-
                                         ticulate  would be higher at  100%  load
                                         than at 60% load  as was the case for the
                                         1978 data. This reversed trend in the 1976
                                         data is believed to be related to difficulties
                                         in operation of the paniculate collector on
                                         unit No. 7  during 1976 and  1977. How-
                                         ever,  it  should be emphasized that the
                                         scale  for the emissions is significantly ex-
                                         panded  and that all  the  emissions  with
                                         100% coal as the only fuel are within 2.8
                                         to 3.9 g/MJ of heat energy input.

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Table 4.    Ames Refuse Processing Plant Paniculate Emissions
                 Roof ventilator
                                                     Roof ventilator
EPA
Run No.
350
351
352
353


32.16
29.77
37.19
23.26

mg/std m3
18.94
36.14
53.80
31.35


20.85
25.27
31.14
9.798
Average standard deviation
Total
71.95
91.18
122.13
64.41
87.42
±25.74


0.516
0.422
0.518
0.343


g/s
0.209
0.453
0.629
0.368



0.449
0.538
0.632
0.201

Total
1.174
1.413
1.779
0.912
1.320
±0.368
  The controlled emissions generally in-
creased with increases in RDF. This result
was expected, since the amount of ash in
the RDF  was  proportionally larger  than
that in the coal. For the 100% coal runs
(0% RDF), the decrease in the emissions
at 80 and 100% load for  the  1978 data
was a result of the repair of the ESP late
in 1977.  Difficulty was experienced with
the ESP during 1976  and 1977.  Some of
the plate  retainers in the ESP had failed,
which rendered them ineffective during
the test runs in 1976 and 1977. This is one
reason why the emissions for the 60, 80,
and 100% loads in 1976 and 1977 appear
to be significantly higher than the  emis-
sions  for the corresponding loads in 1978.
Thus, the data obtained in  1978 are much
more  representative of the  usual perform-
ance  of unit No. 7. Furthermore, the data
of 1978 show very  consistent trends  in the
direction anticipated based  on the fuel in-
put analysis.
  The effect of RDF on ESP collector effi-
ciency drops consistently with increases in
RDF.  These trends were very  consistent
for the data obtained in 1978 and showed
the ESP efficiency to be higher at  80%
load than at 100% load. The effect of the
repair between 1977 and 1978 data is also
apparent in this figure. For example, for
the coal-only runs, the collector efficiency
increased from 93.4 to  94.4%  at  100%
load and from 94.9 to  96.8% at 80%  load,
thus  demonstrating the effect  the  repair
of the ESP had on its performance.
  The oxides of sulfur (SOX) emitted from
the boiler decreased significantly with in-
creases  in  RDF. This  decrease  amounted
to about 50% for 80  and 100%  boiler
loads  in going from 0  to 20% RDF. Thus,
an advantage  of using  RDF with coal is
that relatively high-sulfur coal can be used
and EPA standards can still be met.
  The oxides of nitrogen (NOX)  generally
decreased  with increases  in RDF  at all
boiler loads. The  decrease was in  the
range of  10 to 20% and was somewhat
dependent on  boiler load as the RDF was
increased  up to 20%. The  NOX emissions
generally decreased less for the 1978 data
than for the 1976-1977 data.  This might
represent better operation of the boilers
and better control of the combustion zone
temperatures for the experimental  runs of
1978.
  Except for the 100% load, 20%  RDF
data point, the chloride emissions for the
suspension-fired boiler  increased  linearly
and  significantly with  increases in RDF.
The  boiler experienced as much  as a ten-
fold  increase in chloride emissions as the
RDF increased from 0 to 20% for all boiler
loads in  1978. The  chlorides in  the stack
emissions are believed to have come from
the chlorinated hydrocarbons in  the RDF.
The  chlorides dropped  in the 1976-1977
data because of the dropout of  RDF into
the  bottom hopper;  the bottom grates
had not yet been installed.
  A  series  of 19  trace  elements were
sampled  from all input and output streams
associated  with the operation  of steam
generator unit  No. 7.  Table  5 lists  the
                                trace elements detected in the input fuels
                                of coal and RDF used during the test. The
                                elements selected for analysis are listed by
                                rank  order,  and  the ranking  was  deter-
                                mined by the  concentration given in parts
                                per million (ppm). The standard deviations
                                are also listed. Another column shows the
                                amount of the trace element listed on the
                                basis of mass per unit of energy input to
                                the boiler. The values listed in Table 5 are
                                overall averages for both coal and  RDF.
                                The trace elements with  higher propor-
                                tions of concentration in coal than in RDF
                                are identified  in this table  as strontium,
                                beryllium, nickel,  and  germanium.  The
                                elements that  were not detected based on
                                the  detection limit  of  the analytical in-
                                strumentation  are also indicated. Elements
                                relatively high  in concentration in the RDF
                                were zinc, lead,  copper,  manganese,and
                                vanadium.
                                Conclusions
                                  The major result of this project is  that
                                RDF  can be  burned  successfully  when
                                combined with coal  in both  stoker-fired
                                and  suspension-fired boilers to  produce
                                electric  power. The net cost per mega-
                                gram to produce this RDF fuel was $15.73
                                in 1976,   $12.61 in  1977,  and $12.47 in
                                1978. The yearly reduction in these net
                                costs was due to plant improvements and
                                increased  value of the energy contained in
                                RDF.
                                  Major improvements which  were made
                                in the Ames solid  waste recovery system
Table 5.
Trace Element Content of Coal and RDF Used as Fuel in Boiler Unit No. 7
                   Coal
                                                            RDF
                         Lever*
                                                       Levef
Element
Strontium1'
Vanadium
Manganese
Zinc
Berylliumf
Lead
Tin
Chromium
Nicker*
Copper
Germanium1'
Gallium
Antimony
Selenium
Thallium
Mercury
Arsenic
Cadmium
Cobalt
ppm
86±28
83±16
76±23
66±41
37± 12
36±13
20±5
19±7
18±5
15±3
5.3 ±0.9
2.5±0,5
BDL
BDL
BDL
BDL
BDL
BDL
BDL
ng/J
2.92 ±1.15
2.92± 1. 15
2.92±0.52
2.39± 1.46
1.55±0.49
1.26±0.48
0.71 ±0.17
0.74±0.35
0.63±0.17
0.52±0.08
0.19±0.04
0.09±0.02
BDL
BDL
BDL
BDL
BDL
BDL
BDL
Element
Zinc
Lead
Copper
Manganese
Vanadium
Strontium
Chromium
Tin
Antimony
Gallium
Nickel
Selenium
Cadmium
Germanium
Thallium
Mercury
Arsenic
Beryllium
Cobalt
ppm
763±345
613±289
572±854
194 ±47
154 ±32
46±11
34±8
27 ±8
25±17
16±3
14±4
8±1
6.4±8.1
1.7±0.3
BDL
BDL
BDL
BDL
BDL
ng/J
4.65±2.13
3.89 ±2.27
3.5815.74
1.18±0.33
0.94±0.19
0.28±0.04
0.28±0.04
0.17±0.06
0.15±0.11
0.10 ±0.02
0.09±0.03
0.05±0.01
0.04±0.05
0.01 ±0.00
BDL
BDL
BDL
BDL
BDL
Note: BDL signifies the element is below the analytical instrumentation detection limit.
"Values listed are overall averages for the coal and RDF used during 1978 tests.
''Trace elements with higher proportions in coal than in RDF.

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during  the  three-year   comprehensive
study are as follows:
  • Addition  of  dump  grates  to  the
    35-MW suspension-fired  steam gen-
    erator
  • Relocation of RDF fuel input nozzles
    on  the   35-MW  suspension-fired
    steam  generator to feed  RDF below
    instead of above the coal nozzles
  • Addition  of a grit  removal system  at
    the processing  plant to improve the
    quality of the RDF
  • Addition  of a dust control system  at
    the processing  plant to decrease the
    occurrence  of  failure   of  electric
    motors and  mechanical  equipment,
    as well as to improve the worker en-
    vironment
  • Addition  of two  crew conveyors  at
    the Atlas storage bin  to allow  two
    pneumatic transport  lines to  pick up
    RDF from all four drag conveyors and
    thus reduce the speed of  the pull-ring
    buckets and the wear on the storage
    bin floor
  • Replacement  in 1979 of mechanical
    collectors with new ones  for emis-
    sions  control of the two stoker-fired
    steam  generators  to meet environ-
    mental regulations and permit cofiring
    of RDF and coal in the stoker boilers

  The  study  of  boiler   performance
showed  the  necessity  to  improve the
quality of RDF in order to reduce slagging
and  increase boiler  performance. A grit
removal system was added in  the process-
ing  plant  which  achieved a 24.5%   in-
crease in heating value of the RDF, from
11,408.7 to 14,209.1 kJ/kg, and a 54.5%
decrease in ash, from 20.99 to 9.55%.
Additionally,  the boiler fouling impact  of
RDF was  reduced.
  The addition of the dump grate was the
most significant change. This facilitated
the successful cofiring of RDF with coal
in the suspension-fired steam  generator.
The  relocation of the RDF injection nozzle
to a  point below  the coal injection was
found to   be important  in its effect  on
lowering emissions.
  Suspension-fired   boiler  efficiency
decreased  3.3  percentage  points  when
operating  at  80% steam load  with 20%
heat input from RDF and decreased 1.33
percentage points  at  100%  steam  load
with  20% heat  input  from  RDF.  This
decrease was attributed to an increase in
moisture loss when RDF is  fired. Some
furnace slagging was encountered during
the period prior to  installation of the grit
removal system but was  reduced after the
quality of  the RDF was  improved by the
addition of the grit removal system.
  Stack  paniculate  emissions  increased
slightly  with corresponding increases  in
RDF as a fraction of the fuel input and
was due to the presence of lighter  RDF
particles and increased mass flow. Stack
particulate emissions decreased after the
RDF injection nozzle was relocated below
the coal burners.
  Oxides of nitrogen (NOX) and oxides  of
sulfur  (SOX)  both  decreased  while
chlorides increased with  an increase  in
RDF burning. No discernible trends within
the data scatter were noted concerning
formaldehyde or  hydrocarbon emissons.
Increased emissions of the trace elements
— zinc, copper, lead, and gallium — cor-
responded to increases in RDF.
  The two stoker-fired boiler units,  used
as  backup  to burn RDF, were modified
with new mechanical collectors  in  1979.
These units previously  had  difficulty
meeting  particulate  emission standards
while only  firing coal. Subsequent  tests
conducted on these  units by the City  of
Ames indicated  that coal plus RDF can  be
successfully burned and  meet particulate
emission standards as  a  result  of this
modification along with the grit removal
system at the process plant.
   A. W. Joensen, J. L Hall, J. C. Even, D.  Van Meter. S. K. Adams, P. Gheresus, G.
     Severns, andR. W.  White are with Iowa State University, Ames, IA 50011.
   Michael Black is the EPA Project Officer (see below).
   The complete report, entitled"Co-Firing of Solid Wastes andCoal at Ames: Pulverized,"
     fOrder No. PB 85-183 044/AS; Cost $28.00. subject to change) will be available only
     from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield. VA 22161
           Telephone: 703-487-4650
   The EPA Project Officer can be contacted at:
           Hazardous Waste Engineering Research Laboratory
           U.S. Environmental Protection Agency
           Cincinnati, OH 45268
                                                                              •&U. S. GOVERNMENT PRINTING OFFICE:1985/559 111/10848

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